The invention relates to a rotor for a forced-air-cooled electric motor, in particular a universal motor, especially for use with electrical power tools, with a laminated armature having longitudinal slots and with wire windings of a coil protruding from the longitudinal slots on the front face where the windings form a coil connecting head.
With forced-air-cooled electric motors, in particular electrical power tools, e.g. angle grinders or drilling machines, where particulate dirt, swarf or bore dust emerges in the course of processing, there is, in principle, the problem of an impairment of the rotor coil, in particular the coil connecting head(s) of the rotor coil, since particles and dust are dragged along with the cooling air stream and have an abrasive impact on the rotor coil.
There have already been suggestions made as to how to counter that. With DE 1 613 074 A, it was suggested to cover the coil connecting head of a rotor with a highly absorbent, flexible and porous inlay made of textile fabric, glass fiber or fleece soaked with impregnated resin. This is to achieve a resistant reinforcement of the coil connecting head after hardening.
With DE 196 20 840 A1, it was suggested to apply strip-shaped elements out of felt strips soaked with lacquer or epoxy resin to the coil connecting heads according to their arched form. This is to prevent the particles from impinging on the coil connecting head when the drive of the rotor rotates.
With EP 0 261 306 A2 and DE 298 21 112 U1, it was suggested to provide a cage at one of or both the coil connecting heads, the cage narrowing in a cone- or dome-shaped manner and made of two ring-shaped elements running concentrically relative to the longitudinal axis with inclined rods connecting these elements, the cage being attachable in a rotationally secure manner to the coil connecting head or the laminated armature or the collector and also providing protection against the impact of particles on the coil connecting head when the drive rotates.
The stated solutions are relatively complicated. The task of this invention is to suggest an effective and simple as well as inexpensively realizable protection of rotor coil connecting heads from abrasive wear.